1. Field of the Invention
The specification relates to the field of controls for molecular assays.
2. Description of the Related Art
The accuracy and reliability of assay procedures are typically monitored through the use of controls. These controls include external controls and internal controls, either of which may be used to monitor all or part of the pre-analytical and analytical process.
External controls are performed by parallel analysis of separate samples containing the control substance alongside the test samples. In contrast, an internal control is performed through analysis of both the sample and the control substance in the same vessel and is typically spiked into the test sample prior to or during the testing process. Partial process controls are used to verify the results of specific steps of an assay (e.g., nucleic acid extraction or amplification and detection). In contrast, full process controls are used to verify the results of all steps of the assay (e.g., organism lysis, nucleic acid extraction, amplification and detection).
Each type of control presents advantages and disadvantages. Thus, while a full process control enables utilization of a single control to verify successful completion of each step of the assay, design of a full process control is more demanding than design of a partial process control. Internal full process controls that are introduced into the test sample prior to analysis have been successfully developed for use with molecular assays that rely on mechanical shearing from glass beads to lyse cells. However, for some applications it is not feasible or desirable to employ mechanical lysis and chemical or enzymatic processes must be employed. For example, for the purposes of process automation it may not be practicable to employ a means of mechanical shearing to induce lysis and alternative means must be sought to release cellular components of interest, e.g., nucleic acids, proteins, and the like. Accordingly, many molecular testing systems employ alternative, less generic means of cell lysis other than mechanical shearing. Process controls that are designed for use in the context of mechanical lysis are therefore not necessarily appropriate for control of processes involving alternative, more specific means of cell disruption such as those using chemical or enzymatic treatments that target specific components of the cell wall, membrane or capsule.
One alternate lysing technique relies on the use of the enzyme achromopeptidase (“ACP”). In such a procedure, ACP is used as a component in a solution that lyses cells, and in some cases digests the clinical matrix to facilitate the removal of inhibitors to downstream process steps, including for example, nucleic acid extraction, amplification, and detection. There is a need for internal full process controls for use in connection with processes involving chemical lysing agents, such as ACP.